The invention relates to a method for producing a compound from a plastics material with fixed fibre insert.
EP 0 416 859 B1 discloses an extruding device and a method for mixing fibres and thermoplastic plastics. For this purpose, thermoplastic plastics and discrete lengths of reinforcing fibres are introduced into a screw-type extruder and mixed. After a relatively long mixing path the finished fibre compound arrives in a cutting and handling unit and is processed further there.
In addition, the article "Direktverarbeitung von Endlosfasern auf Spritzgie.beta.maschinen", F. Truckenmuller and H. -G. Fritz, Stuttgart, authors' production run from the journal "Kunststoffe", 82nd year 1992, Carl Hanser Verlag, Munich, describes a method of Bayer AG, Leverkusen, of introducing the reinforcing fibres as filaments, so-called rovings, by means of direct drawing into the screw-type extruder. Accordingly, the thermoplastic plastics material and the dry filaments are introduced into the extruder, cut and mixed, until after a relatively long mixing path the finished fibre compound is produced. EP 0 124 003 B1 is also concerned with this method.
Both methods have the serious disadvantage that a long path is necessary for mixing the plastics material with the fibres. The fibres are repeatedly partially broken in the extruder by means of shearing forces on this long mixing path, which is often also equipped with specific plasticizing and mixing zones, with the result that their length at the output of the extruder is substantially shorter than at the inlet or shortly thereafter. In the quoted article "Direktverarbeitung von Endlosfasern auf Spritzgie.beta.maschinen" the main part of the fibre length in the finished fibre compound is indicated as 1 to 2 mm. However, this is too small for a fibre-reinforced compound with high resistance to breaking.